Buy yourself a standard HS grammar textbook and Strunk and White's. Bust your ass studying them--live in them. And then read good writers as much as you can. And when you aren't busting your ass studying and reading, write. That is the only way.
@John_Scotus
I've had a copy of S&W's since high school. I was in my 30s before I learned the "White" was E.B. White, and that before the 50s it was just Strunk's name on the cover.
@Jeber I lost my hard copy years ago, but still refer to it in my head.
@John_Scotus William Zinser's On Writing Well and Stephen King's On Writing: A Memoir of the Craft are my recommendations.
The product you get by using some of these tools is called "typing." It is just clacking on a keyboard. No one should dare call "writing."